In the hydraulic fracturing (“fracking”) process, it can be desirable that oil and gas operators and the pumping companies that they employ have a full and transparent understanding of the proppant that they are using in the fracking process.
Hydraulic fracturing is the method by which large amounts of proppant, chemicals and water are forced beneath the earth. Fractures are produced in shale deep beneath the earth, and oil/gas that was once trapped is now free to flow.
Proppant, which is the term used to describe the product used to “prop” open the fractures deep within the earth, comes in three main categories: raw fracking sand, resin coated fracking sand, and ceramic proppant. Raw fracking sand is generally considered to be the most widely used. The testing methodology described herein can be applied to all three categories. The testing methodology described herein can also have other uses and benefits.
One aspect of a particular sand product (that is fit for use in fracking) that may be desirable to know is its strength. Sand can be found all over the world, but not every sand grain is created equal. Some sand is much stronger than others, and it is the stronger sands that are usually the most desirable for use in fracking. Strength can be important because it is often desirable that the grains of sand keep the fractures “propped” open to allow oil and gas to flow. If the sand is too weak, it will fracture, break, and/or crush under the enormous pressure beneath the earth, and this in turn will hinder the flow of oil and gas.
Ideally, in a fracking operation, every grain of sand would stay exactly the same, even under enormous amounts of pressure. In other words a grain of sand would not break or crush at all. Ideally, every grain of sand would maintain its original form.
The current testing method is to not test each individual grain size of proppant within a given sample of proppant, but to instead test all of the various grain sizes together. The 25, 30, 35 and 40 mesh sizes of proppant are all placed into a crush cell and pressed together. After the proppant is pressed, the proppant is sieved again using only a sieve having a 40 mesh and pan. The result of this test provides the percentage of material that falls below a sieve having a 40 mesh size and the percentage of material that remains above a sieve having a 40 mesh size.
This method does not give an accurate account of sand that actually broke, chipped, crushed (or otherwise changed in any way). This is because a grain of sand can chip yet the larger portion may not fall below the 40 mesh screen.
The current method generally does not provide a clear score for the proppant to be for decision making purposes, and it generally does not provide an accurate account of the proppant's ability maintain its original form.
An embodiment of the invention disclosed herein can provide a clear and transparent result. An embodiment of the invention can allow users to see if a particular proppant product can maintain its original form under certain amounts of pressure. In other words, a testing method described herein can provide a highly accurate estimate as to what percentage of the proppant will not break or crush in any way.
An example result of an embodiment of a test described herein would be the following:
At 5,000 PSI, the proppant maintained 92.3% of its original form.
At 6,000 PSI the proppant maintained 75.5% of its original form.